Reticulum cell sarcoma (RCS) of the SJL/J mouse has been referred to as a potential model of a Hodgkin's-like lymphoma. A detailed understanding of the progression of growth and the route and time of dissemination of tumor cells will be sought with the aid of models to isolate initial development of a transplantable or primary RCS tumor to the popliteal lymph node. Spread of tumor cells from the initial site and the establishment of secondary foci of tumor growth will be correlated with the appearance of RCS cells in the lymph or peripheral blood and note will be taken of any characteristic of the initial site (degree of lymph node enlargement, tumor cell content, histology) which might serve as an early indicator of probable dissemination. Simultaneously, the tissue localization and degree of entry into lymph of i.v.-injected, highly purified tumor cells will be determined in normal mice and in mice previously given (700-780 r) whole body irradiation. Since x-irradiated mice fail to support multiplication of RCS cells, such irradiated mice will also be used to examine the life span of RCS cells in the absence of cell division. It is possible to reconstitute the ability of an irradiated mouse to support tumor growth by an injection of syngeneic lymphoid cells. It will be determined whether these "tumor growth promoter" cells have the capacity to recirculate. The long-term goal of this research project is to equate the degree of success attained in the radiotherapy of RCS tumors of SJL/J mice to both the radiosensitivity of tumor cells and to the radiosensitivty of the host environmental factors required by the tumor cells for growth and to examine the analogies between these findings and the success of extended field and total lymphoid irradiation over more localized radiotherapy of Hodgkin's patients.